Scientists at West Virginia's Green Bank Observatory have discovered an unfathomably massive neutron star on the verge of collapsing into a black hole. Mind you, when we're talking about neuron stars, we're talking about the densest objects made of matter in the known universe, so "massive" reverts to its scientific meeting. In this case, pulsar J0740+6620 (which is not pictured above) has 2.17 times the mass of our sun... but due to its density, that mass is packed into a tightly-wound little sphere about 30km (18.6 miles) in diameter. The discovery was reported in an article in Nature Astronomy.

The researchers say that the neutron's extreme density likely represents the upper limit for an object's mass before it crushes itself into a black hole. "These city-sized objects are essentially ginormous atomic nuclei," explained Thankful Cromartie, a Grote Reber pre-doctoral fellow at the National Radio Astronomy Observatory in Charlottesville, Virginia and UVA graduate student in a press release. "They are so massive that their interiors take on weird properties. Finding the maximum mass that physics and nature will allow can teach us a great deal about this otherwise inaccessible realm in astrophysics."